1. Field of the Invention
The present invention relates to a scanner driving apparatus for scanning a scanned document by applying a screw (or a ball screw) as dynamics' transference mechanism. Effective scanning range is significantly upgrades, and the scanning accuracy of the scanner can be precisely controlled.
2. Description of the Prior Art
In the present days, many kinds of products are produced and modified each day, and a similar progress also occurs in optical systems such as scanners. There is a trend of mounting a scanner with higher resolution inside a computer case as a standard equipment.
Rollers are conventionally used to feed the scanned document into the scanner, which usually damages the surfaces of the scanned document when the scanned document is feeding. However, the roller-feeding scanner can not scan transparent documents such as lantern slides, and the rollers are easily dirtied by dust that will generate black or unusual color lines in images. In addition, the sizes of the mechanical and optical components are not effectively degraded for achieving the purpose of mounting inside the computer case.
Another common scanning scheme is to put the scanned document inside a tray (or a cassette), and then feeds the scanned document for scanning. The tray (or the cassette) prevents the surface of the scanned document from damaging by directly contacting. Paper jam that usually occurs in the roller-feeding scanner is also overcome. Furthermore, the scheme does not need to clean dust frequently as the roller-feeding scanner does, and the convenience of operation is apparently upgrading.
A transmission axis applied in a conventional scanner usually constrains scanning range of a scanner. FIGS. 5A and 5B respectively represent a cross-sectional and a top view of the conventional scheme while applying the transmission axis and a wire as dynamics' transference mechanism. A tray 501 connects the wire 503 with a fix 506 and a support 504, wherein the fix 506 receives the dynamics from the wire 503, and the support 504 is used as support mechanism. Under controlled by the fix 506, the tray 501 gets in and out of the scanner. All the allocations of the gear sets 502, the wire 503, the transmission axis 505, and the support 504 are outside the tray 501, which constrain the effective scanning range of the traditional scanner.
All skilled know that the sizes of the gear sets and the motors must follow a certain constraint, and furthermore, the sizes of the optical elements can not be effectively reduced. It implies that almost all the build-in scanners with the scanning area about 4 inches.times.6 inches. What is clearly needed is a scanner being capable of larger scanning range and more accurate control.